This invention relates generally to a method and apparatus for machining rough edged wooden workpieces into parallelograms. The invention relates more specifically to the method and apparatus for machining wooden workpieces having rough edges at varying angles from the top and bottom surfaces and variable widths into the shape of parallelograms having substantially flat surfaces and maximum cross sectional areas.
In the lumber industry, when a cylindrical log is cut into a plurality of longitudinally extending pieces at least some of the pieces will have curvilinear edges. Since lumber is normally used in rectangular form the curvilinear edges must be removed by a machining process known as edging. Generally, edging refers to that process whereby a rough piece of lumber has its opposed rough edges machined to flat surfaces at some predetermined width. Common dimension lumber is generally sold in 4, 6, 8, 10, and 12 inch widths and therefore the edging process will usually yield one of these dimensions. The object in edging boards is to produce a rectangular piece having the maximum obtainable width consistent with given edging rules and product requirements.
In the process of cutting a log into a plurality of sector-shaped pieces and then bonding two similarly sized sector-shaped pieces together to a predetermined thickness, thin edge to thick edge, to form a board in the shape of a rough parallelgram, it becomes necessary as a subsequent step in making usable lumber, to edge the opposed sides of the rough parallelogram. By edging the rough parallelogram, it is meant that the two opposed slanting edges of the composite board will be machined into parallel flat surfaces according to a substantially automatic dimension maximizing process. After the composite boards are edged to their maximum obtainable width, a plurality of them having appropriate dimensions can then be edge bonded together to form wider width composite members. Such a process is substantially less wasteful of wood fiber and results in a considerably higher yield of lumber from a given log, especially smaller logs. The process of forming composite lumber products from sector-shaped pieces is fully disclosed in the commonly assigned U.S. Pat. No. 3,961,654. A similar process where rough parallelograms would be formed is disclosed in U.S. Pat. No. 3,903,943 also commonly assigned. The disclosures of the commonly assigned U.S. patents are incorporated herein by reference in order to provide a complete description and understanding of the present invention.
Two variables in the resulting rough parallelograms must be considered in the edging process. One is the width of the parallelogram and the other is the angle formed between a longitudinal plane normal to the top and bottom surfaces and a longitudinal plane passing through the top and bottom edges on each side of the parallelogram. These variables are caused by cutting sector-shaped pieces from logs of varying diameter. While the rough parallelograms will have substantially the same thickness, the width and above defined angle may vary. Accordingly, an apparatus to carry out the edging process must be capable of adjustment to account for the two variables. Ideally, the adjustments will be made automatically based on upstream sensing of the variables and control of the cutter heads making the edging cuts.
In a production environment it is desirable to provide for continuous operation where the workpieces will be traveling at an efficient rate of speed while the variables are sensed and the edging step carried out. Reliability of the equipment is also desirable as is a low capital cost.
Accordingly, from the foregoing, the primary object of the present invention is to machine from a rough elongated workpiece a surfaced piece having flat surfaces with the maximum obtainable width and in the shape of a parallelogram.
Another object of the present invention is to carry out such a machining or edging step in a substantially automatic manner.
These and other objects of the present invention will become apparent upon reading the following specification while referring to the attached drawing.